The present invention relates to methods of and arrangements for mining.
More particularly, the present invention concerns methods of and arrangements for extraction of minerals such as rock, coal, etc. in mining galleries.
It is known in the prior art to use for extraction purposes a mechanical cutting tool (i.e. chisel) together with high pressure fluid medium jets. The fluid medium jets are directed in the cutting direction of the cutting tool and more or less normal to a surface of material to be mined. The cutting tool has a cutting edge for cutting into the material to be mined. The fluid medium jets are so guided as to exit the arrangement in the region adjacent to the cutting edge of the cutting tool.
It has been recognized that the extraction productivity of the cutting tool with the high-pressure fluid medium jets is considerably superior to that of the cutting tool without the high-pressure fluid medium jets.
At the same time, the use of the fluid medium considerably increases the service life of the mechanical cutting tool per se. In other words, the fluid medium reduces the abrasion (i.e. wear) of the cutting tool.
During the extraction process, the cutting edge of the cutting tool cuts into a surface of material to be mined so that small fissures develop in the bottom of the cut. The high pressure fluid medium jets are directed (with an extremely high kinetic energy) against the surface to be cut so that the fluid jets enter the small fissures. Due to the extremely high pressure the fluid jets function as a "hydraulic wedge" inserted into the fissures. Thus, the fluid jets considerably increase the depth of the fissures. Obviously, the penetration of the mechanical cutting tool in the surface to be cut is facilitated, since the actual resistance of the material against penetration is reduced. The high pressure fluid medium (e.g. the pressure is up to many thousand bars) continuously flushes the material particles outwardly away from the cut (i.e. fissures) so as to clean the passage for the cutting tool.
The fluid medium cools the cutting tool during the extraction process, which fact considerably increases te service life of the cutting tool. In fact, the fluid medium reduces the temperature of the cutting edge when the latter cuts the surface of the material to be mined. Such an intensive cooling affect reduces the abrasion of the cutting edge even if the extraction process is conducted in a very hard and abrasive material.
The method of mining is not limited only to the mining galleries (however, it is considered to be the most advantageous use) where the cutting is conducted along a predetermined profile (i.e. so-called "contour cutting") which is determined by the cross-section of the gallery. The same method may be used for extraction of the minerals by way of scraping the surface of material to be mixed. This is especially advantageous in the case of coal mining by means of planning tools or coal augers.
The known methods of and arrangements for mining are not satisfactory with respect to the requirements made to reliability and quality of mining under various circumstances and conditions. The penetration of the fluid medium into the material to be cut is not satisfactory, for example if the fluid medium jets are directed as extremely thin streams (e.g. of an outlet diameter of the jet constitutes 0.2-0.8 mm and the pressure of the fluid medium jet is 3500 bars) and of the cutting speed of the cutting tool is inadequately increased. It is especially true when the material to be mined constitutes a very hard substance. However, should the cutting speed be correspondingly reduced, then the penetration of the fluid medium jets may be increased, depending on the resistance of the actual material against the penetration, up to 30 mm. Nevertheless, the cutting speed of 0.2 m/s appears in most cases somewhat too small in order to obtain the best possible use of the arrangement.